U.S. patent application number 10/917186 was filed with the patent office on 2005-04-21 for color filter panel and liquid crystal display including the same.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Rho, Soo-Gyu.
Application Number | 20050083452 10/917186 |
Document ID | / |
Family ID | 34464701 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050083452 |
Kind Code |
A1 |
Rho, Soo-Gyu |
April 21, 2005 |
Color filter panel and liquid crystal display including the
same
Abstract
An LCD comprising a first substrate having an inner surface and
an outer surface; a green color filter formed on the outer surface
of the first substrate; red, green, and blue color filters formed
on the inner surface of the first substrate; a second substrate
facing the first substrate and having an inner surface and an outer
surface; a pixel electrode formed on the inner surface of the
second substrate; a common electrode formed on the inner surface of
one of the first and second substrates; and a liquid crystal layer
disposed between the first substrate and the second substrate is
provided. By this structure, a green light having nigh color purity
is produced. The manufacturing method of an LCD is simplified by
replacing the black matrix with the overlapped color filters.
Inventors: |
Rho, Soo-Gyu; (Suwon-si,
KR) |
Correspondence
Address: |
F. CHAU & ASSOCIATES, LLC
130 WOODBURY ROAD
WOODBURY
NY
11797
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
|
Family ID: |
34464701 |
Appl. No.: |
10/917186 |
Filed: |
August 10, 2004 |
Current U.S.
Class: |
349/106 |
Current CPC
Class: |
G02F 1/133514
20130101 |
Class at
Publication: |
349/106 |
International
Class: |
G02F 001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 16, 2003 |
KR |
2003-72092 |
Claims
What is claimed is:
1. A liquid crystal display comprising: a first substrate having an
inner surface and an outer surface; a green color filter formed on
the outer surface of the first substrate; red, green, and blue
color filters formed on the inner surface of the first substrate; a
second substrate facing the first substrate and having an inner
surface and an outer surface; a pixel electrode formed on the inner
surface of the second substrate; a common electrode formed on the
inner surface of one of the first and second substrates; and a
liquid crystal layer disposed between the first substrate and the
second substrate.
2. The liquid crystal display of claim 1, wherein the green color
filter formed on the outer surface of the first substrate is
disposed on all the display area except at red and blue pixel
areas, the green and blue color filters formed on the inner surface
of the first substrate are respectively disposed on green and blue
pixel areas, and the red color filter formed on the inner surface
of the first substrate is disposed on all the display area except
at the green and blue pixel areas.
3. The liquid crystal display of claim 2, wherein the green color
filter formed on the outer surface of the first substrate is at
least 2.5 times thicker than the green color filter formed on the
inner surface of the first substrate.
4. A color filter panel comprising: a transparent insulating
substrate having two surfaces; a green color filter formed on a
first substrate of the insulating substrate; and red, green, and
blue color filters formed on a second surface of the insulating
substrate, wherein the green color filter formed on the first
surface is removed at predetermined areas to expose the first
surface of the insulating substrate, the red color filter formed on
the second surface is disposed everywhere except at the areas where
the green and blue color filters are disposed, and the red and blue
color filters formed on the second surface are seen through the
predetermined areas exposing the first surface of the insulating
substrate.
5. The color filter panel of claim 4, further including a
transparent electrode formed on the red, green, and blue color
filters.
6. The color filter panel of claim 4, wherein the thickness of the
green color filter formed on the first surface is 2.5 times the
thickness of the green color filter formed on the second surface.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present disclosure relates to liquid crystal displays
(LCDs), and in detail, to a method for improving display quality
and viewing angle of LCDs.
[0003] (b) Description of the Related Art
[0004] An LCD includes two panels provided with field-generating
electrodes, and a liquid crystal (LC) layer interposed
therebetween. The LCD displays images by applying voltages to the
field-generating electrodes to generate an electric field in the LC
layer, which determines orientations of LC molecules in the LC
layer to adjust polarization of incident light.
[0005] In an LCD, usually, red, green, and blue color filters are
sequentially disposed. Color images are displayed by controlling
intensity of light which passes through the color filters.
[0006] However, there are limitations in displaying full colors by
using three color filters.
[0007] Recently, as LCDs have been gaining popularity as
multi-media displays, the need for good color reproducibility has
increased. Especially, when an LCD is used as a television, good
color reproducibility is extremely important.
[0008] When color reproducibility is discussed, the green color is
most important. The green color of the National Television
Standards Committee (NTSC) is marked at x=0.21, y=0.70 on color
coordinates of the International Commission of Illumination (CIE).
However, the green light from the conventional green color filter
of an LCD television having a thickness of 1.9 .mu.m is marked at
x=0.275, y=0.60 on the CIE color coordinate system.
[0009] When the conventional green color filter is used, the color
reproducibility reaches only up to 72% of natural color. If one
wishes to make a green color filter producing green color of NTSC
which allows color reproducibility of 80% to 100%, one of the
following two methods may be used. The first is increasing the
dispersion density of pigments in the color filter, and the second
is increasing the thickness of the color filter. However, when the
dispersion density of pigments in the color filter is increased,
stability of the photoresist of the color filter is degraded. When
the thickness of the color filter is increased, the color filter
needs to have a thickness of about 7.6 .mu.m, which is four times
thicker than that of the normal color filter. This causes
difficulty in forming the color filter.
SUMMARY OF THE INVENTION
[0010] To solve such a problem, the present invention comprises a
color filter panel having green color filters on both sides
thereof.
[0011] In more detail, a liquid crystal display comprising a first
substrate having an inner surface and an outer surface; a green
color filter formed on the outer surface of the first substrate;
red, green, and blue color filters formed on the inner surface of
the first substrate; a second substrate facing the first substrate
and having an inner surface and an outer surface; a pixel electrode
formed on the inner surface of the second substrate; a common
electrode formed on the inner surface of one of the first and
second substrates; and a liquid crystal layer disposed between the
first substrate and the second substrate is provided.
[0012] The green color filter formed on the outer surface of the
first substrate may be disposed on the whole display area except at
red and blue pixel areas, the green and blue color filters formed
on the inner surface of the first substrate are respectively
disposed on green and blue pixel areas, and the red color filter
formed on the inner surface of the first substrate is disposed on
the whole display area except at the green and blue pixel
areas.
[0013] The green color filter formed on the outer surface of the
first substrate may be at least 2.5 times the thickness of the
green color filter formed on the inner surface of the first
substrate.
[0014] A color filter panel comprising a transparent insulating
substrate having two surfaces; a green color filter formed on a
first surface of the insulating substrate; and red, green, and blue
color filters formed on a second surface of the insulating
substrate, wherein the green color filter formed on the first
surface is removed in predetermined areas to expose part of the
first surface of the insulating substrate, the red color filter
formed on the second surface is disposed on the area except at the
areas that the green and blue color filters are disposed, and the
red and blue color filters formed on the second surface are seen
through the predetermined areas exposing the first surface of the
insulating substrate is provided.
[0015] The color filter panel may further include a transparent
electrode formed on the red, green, and blue color filters. The
thickness of the green color filter formed on the first surface may
be 2.5 times the thickness of the green color filter formed on the
second surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other advantages of the present invention will
become more apparent by describing preferred embodiments thereof in
detail with reference to the accompanying drawings, in which:
[0017] FIG. 1 is a sectional view of a liquid crystal display (LCD)
according to an exemplary embodiment of the present invention;
[0018] FIG. 2 is a layout view of the color filter panel of the LCD
according to the exemplary embodiment of the present invention
shown from the top side;
[0019] FIG. 3 is a layout view of the color filter panel of the LCD
according to the exemplary embodiment of the present invention
shown from the bottom side;
[0020] FIG. 4 shows spectrum graphs of a light passing through a
1.9 .mu.m green color filter and a light passing through a green
color filter according to an exemplary embodiment of the present
invention; and
[0021] FIG. 5 shows spectrum graphs of three kinds of light
respectively passing through three kinds of color filters according
to an exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. The present
invention may, however, be embodied in many different forms and
should not be construed as limited to the embodiments set forth
herein.
[0023] In the drawings, the thickness of layers, films, and regions
are exaggerated for clarity. Like numerals refer to like elements
throughout. It will be understood that when an element such as a
layer, film, region, or substrate is referred to as being "on"
another element, it can be directly on the other element or
intervening elements may also be present. In contrast, when an
element is referred to as being "directly on" another element,
there are no intervening elements present.
[0024] Now, liquid crystal displays according to embodiments of the
present invention will be described with reference to the
accompanying drawings.
[0025] FIG. 1 is a sectional view of a liquid crystal display (LCD)
according to an exemplary embodiment of the present invention. FIG.
2 is a layout view of the color filter panel of the LCD according
to the exemplary embodiment of the present invention shown from the
top side. FIG. 3 is a layout view of the color filter panel of the
LCD according to the exemplary embodiment of the present invention
shown from the bottom side.
[0026] An LCD according to an exemplary embodiment includes a thin
film transistor (TFT) array panel 100, a color filter panel 200
facing the TFT array panel 100, a liquid crystal layer disposed
between the two panels 100 and 200, a pair of compensation films 11
and 21 respectively disposed on the outside of the two panels 100
and 200, and a pair of polarizing films 12 and 22 respectively
disposed on outside of the two compensation films 11 and 12.
[0027] The TFT array panel 100 will now be described in detail.
[0028] A plurality of pixel electrodes 190 made of indium tin oxide
(ITO) or indium zinc oxide (IZO) are formed on a transparent
substrate such as glass. Each pixel electrode 190 is connected to a
TFT which is a switching element and is applied an image signal
voltage through the TFT. Here, the TFT has a gate electrode
connected to a gate line (not illustrated) transmitting scanning
signals, a source electrode connected to a data line (not
illustrated) transmitting image signals, and a drain electrode
connected to the pixel electrode 190 that switches the image
signals according to the scanning signals.
[0029] For a reflective LCD, the pixel electrode 190 is formed of a
reflective metal instead of a transparent material, and the lower
polarizing film 12 and the lower compensation film 11 are
omitted.
[0030] Next, the color filter panel 200 will be described in
detail.
[0031] Red, green, and blue color filters 230R, 230G, and 230B and
a common electrode 270 made of a transparent conductive material
such as indium tin oxide (ITO) or indium zinc oxide (IZO) are
formed on the lower surface of an upper substrate 210 made of a
transparent insulating material such as glass.
[0032] Here, the green color filter 230G and the blue color filter
230B are respectively formed on the corresponding pixel areas. The
red color filter 230R is formed on the whole display area except at
the areas of the green and blue color filters 230G and 230B, but
including the red pixel area.
[0033] The thicknesses of the color filters 230R, 230G, and 230B
are about 1.9 .mu.m.
[0034] A green color filter 230G is formed on the upper surface of
the upper substrate 210.
[0035] The green color filter 230G formed on the upper surface of
the upper substrate 210 is disposed on the whole area of the
display area except at the areas of the red and blue pixels.
[0036] Here, the display area means an area to display images in an
LCD. The green color filter 230G formed on the upper surface of the
upper substrate 210 has a thickness of about 5.7 .mu.m.
[0037] The thickness of the color filters formed on the lower and
upper surfaces of the upper substrate 210 may be modified according
to their properties. However, under any circumstances, the
thickness ratio of the green color filter on the lower surface to
that on the upper surface is preferably over 1:2.5.
[0038] As described above, when the green color filter 230G is
formed on the upper surface of the upper substrate 210, and the
red, green, and blue color filters 230R, 230G, and 230B are formed
on the lower surface of the upper substrate 210, a red light and a
blue light are respectively produced by the red color filter 230R
and the blue color filter 230B having thicknesses of about 1.9
.mu.m in the red and blue pixels, and a green light having high
color purity is produced by the green color filters 230G having a
total thickness of about 7.6 .mu.m in the green pixel. The red
color filter 230R and the green color filter 230G overlap each
other to block almost all of the light in the areas between the
pixel areas and the area around the display area. The overlapped
red and green color filters 230R and 230G play a role of a black
matrix.
[0039] The lower polarizing film 12 and the upper polarizing film
22 are preferably disposed to make their polarizing axes
perpendicular to each other. Under such polarizing films
disposition, the LCD shows a normally black mode such that black is
displayed when there is no electric field in the liquid crystal
layer
[0040] According to the present invention, the green color filter
230G can have sufficient thickness since the green color filters
230G are formed on both side of the color filter panel 200. Such a
green color filter having sufficient thickness can produce a green
light having high color purity.
[0041] FIG. 4 shows spectrum graphs of a light passing through a
1.9 .mu.m green color filter and a light passing through a green
color filter according to an exemplary embodiment of the present
invention.
[0042] In FIG. 4, curve A represents a spectrum graph of a light
passing through 1.9 .mu.m green color filter, and curve B
represents a spectrum graph of a light passing through a green
color filter according to an exemplary embodiment of the present
invention.
[0043] As shown in FIG. 4, the spectrum of the green light produced
by the green color filter according to the present invention is
distributed in a narrower wavelength range than that of the green
light produced by a conventional green color filter having a
thickness of 1.9 .mu.m.
[0044] The overlapped red and green color filters 230R and 230G
replace the black matrix in the exemplary embodiment of the present
invention. The reason why the overlapped red and green color
filters 230R and 230G can play a role of a black matrix will be
described with reference to FIG. 5.
[0045] FIG. 5 shows spectrum graphs of three kinds of lights
respectively passing through three kinds of color filters according
to an exemplary embodiment of the present invention.
[0046] As shown in FIG. 5, the green color filter 230G of the
exemplary LCD according to the present invention is a band pass
filter of wavelengths ranging from 495.about.580 nm, and the red
color filter 230R is a high pass filter of wavelengths of 580 nm or
longer. According, when a white light passes through both the green
and red color filters 230G and 230R, all the light will be blocked
by the color filters 230G and 230G to display black.
[0047] As described above, in the present invention, a green light
having high color purity is produced by forming the green color
filters on both sides of the upper substrate 210. The manufacturing
method of an LCD is simplified by replacing the black matrix with
the overlapped color filters 230R and 230G.
[0048] Although preferred embodiments of the present invention have
been described in detail hereinabove, it should be clearly
understood that many variations and/or modifications of the basic
inventive concepts herein taught which may appear to those skilled
in the present art will still fall within the spirit and scope of
the present invention, as defined in the appended claims.
* * * * *